• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.12C
• /
• pp.1181-1185
• /
• 2005

A combining of MIMO signal processing with OFDM is regarded as a promising solution of enhancing the performance of next generation wireless system. Therefore, in this paper, an OFDM-based wireless system employing layered space-time architecture is considered for a high-rate transmission. In the MIMO-OFDM system, we evaluate the PAR performance using the SLM approaches. The investigated SLM scheme for MIMO-OFDM signals selects the transmitted sequence with lowest average PAR over all transmitting antennas and retrieves the side information very accurately at the expense of a slight degradation of the PAR performance. The low probability of false side information can improve the overall detection performance of the MIMO-OFDM system with erroneous side information compared to the ordinary SLM approache, respectively. Also, we provide closed form of the average BER performance in MIMO-OFDM system using analytic approach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.4A
• /
• pp.378-383
• /
• 2004

Orthogonal Frequency Division Multiplexing (OFDM) transmits high-speed data by splitting the transmission bandwidth into a number of subcarriers. The bandwidth of each subcarrier is ensured to be smaller than the coherence bandwidth. This paper presents an OFDM system incorporated with the Carrier Interferometry (CI) codes to improve the performance by enhancing frequency diversity effect. The performances of CI-OFDM with multilevel modulations are investigated in highly dispersive fading channels. For the investigation of performance improvement of CI-OFDM, a simulator has been developed using a well-known SPW simulation platform. The simulation results show that the CI-OFDM provides both performance improvement and robustness against dispersive fading channel behavior. The performance of CI-OFBM with multilevel modulations demonstrates that CI-OFDM outperforms a traditional OFDM system, particularly in highly dispersive channels. With a relatively large delay spread of 151㎱ compared to the guard interval of 800㎱, CI-OFDM provides a BER of 10$^{-3}$ if sufficient signal power is present.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.3C
• /
• pp.224-231
• /
• 2003

In this paper we proposed system parameter values of ultra-wideband Impulse Radio systems for the frequency band(3.1~10.6GHz), which is allocated by Federal Communications Commission(FCC). We also analyzed performance of the proposed system in the multiple access interference environment. According to result, application of possible pulse duration($t_{n}$) is very limited by 0.04~0.0326 ns in permission frequency range that establish in FCC. In the case of the same pulse signal power, we could know that system performance was changed by pulse repetition number($N_{s}$ ) regardless of pulse duration. Thus, We could know that we have to need duration of monocycle pulse and setting of frame un it time(Τ$_{f}$ ) according to multi user numbers and design proper pulse repetition number by transfer rate in multiple access systems design. In the IR system that needs high speed transmission more than 50 Mbps in multiple access interference environment, we could know that very serious performance decrease by multiple access interference happens. Therefore, as the design of high speed multiple access IR system, it should be designed to additional improvement techniques that can remove multiple access interference at the same time.

• Journal of Communications and Networks
• /
• v.14 no.2
• /
• pp.188-194
• /
• 2012

Cognitive networks (CNs) are capable of enabling dynamic spectrum allocation, and thus constitute a promising technology for future wireless communication. Whereas, the implementation of CN will lead to the requirement of an increased energy-arrival rate, which is a significant parameter in energy harvesting design of a cognitive user (CU) device. A well-designed spectrum-sensing scheme will lower the energy-arrival rate that is required and enable CNs to self-sustain, which will also help alleviate global warming. In this paper, spectrum sensing in a multi-user cognitive ad hoc network with a wide-band spectrum is considered. Based on the prospective spectrum sensing, we classify CN operation into two modes: Distributed and centralized. In a distributed network, each CU conducts spectrum sensing for its own data transmission, while in a centralized network, there is only one cognitive cluster header which performs spectrum sensing and broadcasts its sensing results to other CUs. Thus, a wide-band spectrum that is divided into multiple sub-channels can be sensed simultaneously in a distributed manner or sequentially in a centralized manner. We consider the energy consumption for spectrum sensing only of an analog-to-digital convertor (ADC). By formulating energy consumption for spectrum sensing in terms of the sub-channel sampling rate and whole-band sensing time, the sampling rate and whole-band sensing time that are optimal for minimizing the total energy consumption within sensing reliability constraints are obtained. A power dissipation model of an ADC, which plays an important role in formulating the energy efficiency problem, is presented. Using AD9051 as an ADC example, our numerical results show that the optimal sensing parameters will achieve a reduction in the energy-arrival rate of up to 97.7% and 50% in a distributed and a centralized network, respectively, when comparing the optimal and worst-case energy consumption for given system settings.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.4C
• /
• pp.329-337
• /
• 2012

Capsule Endoscope(CE) is a capsule-shaped electronic device which can examine the lesions in digestive tract of human body. Recently the medical procedure using capsule endoscope is receiving great attention to both doctors and patients, since the conventional push-typed endoscope using cables brings great pain and fear to the patients. The technique was firstly available in 2000 and is based on a convergence techniques among BT(Bio Technology), IT(Information Technology), and NT(Nano Technology). The device consists of an optical parts including LEDs(Light Emitting Diodes), an image sensor, a communication module and a power module. Capsule endoscope is the embodiment of the state-of-the art technology and requires key technologies in the various engineering fields. Therefore, in this paper, we introduce the composition of the capsule endoscope system, and compare the communication method between RF(Radio Frequency) communication and HBC(Human Body Communication), which are typically used for data transmission in the capsule endoscope. Furthermore, we analyze the specification of commercialized capsule endoscopes and present the future developments and technical challenges.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37A no.9
• /
• pp.721-727
• /
• 2012

Since a conventional multi-cell transmit diversity scheme depends on the feedback from the user for the channel gain information, its performance gets to severely degrade when the channel varies fast due to the high mobility of the user. Also, transmit power of the base station cannot be fully used in the conventional scheme because only one transmit antenna is used for data transmission. In this paper, we propose a multi-cell transmit diversity scheme appropriate for fast fading channel. In the proposed scheme, channel-independent precoding vector is applied over all transmit antennas and different precoding vectors are applied for neighboring subcarriers so that the received signal is avoided to experience deep fading over multiple neighboring subcarriers. Simulation results show that the proposed scheme has better detector output signal-to-noise ratio (SNR) and bit error rate (BER) performances than the conventional scheme.

• Resources Recycling
• /
• v.22 no.5
• /
• pp.63-70
• /
• 2013

There are generated the hundreds of tons of waste electric wire per year due to replace for increase transmission capacity and/or replacement of old electric wire by Korea's national power grid and/or private industrial factories. Recently, the wire recycling technologies studied extensively in terms of effieiency by of economic aspects and environment aspects. In this paper, the patents and papers for the recycling technologies of spent electric wire were collected and analyzed. The range of search was limited in the open patents of USA (US), European Union (EP), Japan (JP), Korea (KR) and SCI journals from 1975 to 2011. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals were analyzed by the years, countries, companies, and technologies.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.12
• /
• pp.1329-1336
• /
• 2015

Due to the advances in hardware technologies for low-power CMOS cameras, there have been various researches on wireless video sensor network(WVSN) applications including agricultural monitoring and environmental tracking. In such a system, its core technologies include video compression and wireless transmission. Since data of video sensors are bigger than those of other sensors, it is particularly necessary to estimate precisely the traffic after video encoding. In this paper, we present an estimation method for the encoded video traffic in WVSN networks. To estimate traffic characteristics accurately, the proposed method first measures complexities of frames and then applies them to the bit rate estimation adaptively. It is shown by experimental results that the proposed method improves the estimation of bit rate characteristics by more than 12% as compared to the existing method.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.6
• /
• pp.857-870
• /
• 2017

The use of shield TBM is gradually increasing due to the urbanization of social infrastructures. Reliable estimation of advance rate is very important for accurate construction period and cost. For this purpose, it is required to develop the prediction model of advance rate that can consider the ground properties reasonably. Based on the database collected from field, statistical prediction procedure for field penetration index (FPI) was modularized in this study to calculate penetration rate of shield TBM. As output parameter, FPI was selected and various systems were included in this module such as, procedure of eliminating abnormal dataset, preprocessing of dataset and ridge regression with best subset selection. And it was finally validated by using field dataset.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.6
• /
• pp.49-59
• /
• 2014

Recently, wireless sensor networks(WSNs) are widely used for intrusion detection and ecology, environment, atmosphere, industry, traffic, fire monitoring. In this paper, an energy efficient clustering algorithm is proposed. The proposed algorithm forms clusters uniformly by selecting cluster head that optimally located based on receiving power. Besides, proposed algorithm can induce uniform energy consumption regardless of location of nodes by multi-hop transmission and MST formation with limited maximum depth. Through the above, proposed algorithm elongates network life time, reduces energy consumption of nodes and induces fair energy consumption compared to conventional LEACH and HEED. The results of simulation show that the proposed clustering algorithm elongates network life time through fair energy consumption.